Existing exposure systems for laboratory animals are of two main types. The first is a large chamber in which a considerable number of animals are contained in groups and the entire body exposed to a flow of gaseous material. Such chambers are exemplified by those shown in U.S. Pat. Nos. 4,216,741 and 4,398,498. In another type exemplified by U.S. Pat. No. 4,721,660, the animals are individually contained in relatively small chambers and the gaseous material is supplied in such a manner that only the nose and closely adjacent portions of the animal receive the gas or aerosol. The need has arisen, however, for systems which are more versatile in that they can be used for whole-body exposure or nose-only exposure as desired. It is particularly desirable that the system be suitable for simultaneously exposing some animals to the whole-body treatment and others to the nose-only in order to determine possible differences in effect depending on the mode of exposure to the same atmosphere. This invention is adapted to accomplish those objectives.
U.S. Pat. No. 4,721,060 referenced above discloses an exposure system of the "nose-only" type. In this system gaseous material from a central chamber flows through a number of small tubes to the inlet of bottles in which the experimental animals are contained. Gas is drawn from these bottles to an outer chamber from which it is exhausted to a disposal system. The present system operates in the same general manner as the prior system, but at least some of the bottles or other containers for the animals are so designed that the gas or aerosol passes over the entire body of the animal before going into the exhaust chamber. Since the basic system is the same, it is only necessary to interchange the type of animal containers in order to change between nose-only and whole-body exposure of the animals. As a secondary matter, the invention includes improvements in the circulation system for the atmosphere to which the animal is exposed.
In more detail, the animal container is, in general, of the bottle type but contains a wire cage or wire mesh restrainer or holder which is spaced from the walls of the bottle so that gaseous material may flow about the entire animal. A return passage is provided from the end of the container back to the exhaust manifold. Preferably, this is accomplished by making the container of double-walled construction with the inner wall forming the primary container and connected to the inlet manifold and the space between the walls connected to the exhaust manifold. The inner wall terminates short of the outer wall and is open at its end remote from the manifolds. The inlet and exhaust manifolds may be concentric as described in the above U.S. Pat. No. 4,721,060, or they may be of box-like (and/or) tubular construction. The choice will depend on the particular laboratory environment in which the system is to be used.
In one embodiment of the last named type, the animal container and the inlet tubes supplying the gas to the animals and the exhaust ports leading from the containers are arranged in vertical columns. A tubular horizontal inlet manifold extends along the top, and vertical sub-manifolds are connected to the inlet manifold. Valve connections extend from the inlet manifold to each of the vertical sub-manifolds so that gas or aerosol can be supplied selectively to any or all of the columns of containers. A single large exhaust manifold surrounds the inlet tubes and is connected to the exhaust ports from the containers. The entire system may be mounted on a cart for ready movement about the laboratory.